World War I or "The Great War" as it was better known by--was considered the war to end all wars. The death toll was tremendous, as new battle technology such as machine guns, poison gas, and airplanes created death in mass.

This truly was a world war, as it included fighting on nearly every continent, thanks in part to European colonial empires. The causes that led to WWI had been building up for many years and were finally set off by the rejection of the Austrian "ultimatum" by Serbia, after the assassination of Austrian Archduke Franz Ferdinand.

For its part, the US was slow to enter WWI. Many American citizens considered this a European conflict and most were eager to remain "Isolationist." However, this would not last forever. The combination of our friendly alliance with Great Britain and a series of transgressions by Germany led the US to the side of the Allied Powers.

The biggest impact for the US was the war's affect on home life. With many men going overseas to fight, a large influx of African Americans came to northern cities in a mass movement called "The Great Migration." Women also shouldered greater responsibility, which ultimately led to the ratification of the 19th Amendment in 1920.

Not all of the changes were considered positive. The US federal government's powers increased to an all-time high with the passage of the Espionage and Sedition Acts which essentially made it illegal to criticize the government or the war effort.

WWI had a profound impact on the United States' place in the world. It further connected us to the affairs of the European continent and it also made us more isolated in the process. A real "catch-22."

New countries after WWI: Carved out of German, Austrian, Ottoman, and Russian Territory.